Long-term, undiagnosed, vitamin B12 deficiency can CAUSE neuropathy (and, at the very least, contribute to it)!!! This is especially true if you have elevated folate, which is masking the vitamin B12 deficiency. WHEN THIS HAPPENS, IT IS CALLED "FUNCTIONAL" B12 DEFICIENCY. Your B12 numbers can actually be within range or low-normal, but your body cannot use the B12 the way it was intended. This is what happened to me and it went undiagnosed 7 years. I now have irreparable nerve damage. You should feel markedly better after several weeks with the B12. I had no idea how debilitating the complications from B12 deficiency could be. You should look at some of the youtube videos on "Long-term complications from b12 deficiency", and see if those line up with what you're experiencing. If you are like me, and think you may have "functional" b12 deficiency, ask your physician for an MMA (methylmalonic acid) blood test. This will prove whether you have a functional b12 deficiency. Best of luck